From the Old Farmers Almanac here.
Shrubs that form their flower buds on “new” wood (i.e., growth that will occur in the coming spring). Prune these in the winter and early spring. Examples include:
- abelia,
- beautyberry,
- butterfly bush,
- most clematis,
- smooth hydrangeas,
- panicle hydrangeas,
- potentilla,
- roses,
- rose-of-sharon,
- shrub dogwoods,
- Japanese spirea,
- St. Johnswort, and
- summersweet.
Shrubs that bloom on “old” wood (i.e., growth from the previous year). Wait until late spring or early summer (after flowers fade) to prune shrubs that bloom on “old” wood. If you cut them too early, you’ll cut off the buds that would’ve opened this spring! The best time to prune spring-blooming shrubs is right after the spring blooms fade. Examples are:
- azalea,
- beautybush,
- bridalwreath spirea,
- spring-blooming clematis,
- cotoneaster,
- deutzia,
- enkianthus,
- flowering almond,
- forsythia,
- mophead hydrangeas,
- lilacs,
- mock orange,
- mountain laurel,
- ninebark,
- oakleaf hydrangea,
- pieris,
- rhododendron,
- viburnum,
- Virginia sweetspire,
- weigela,
- wisteria, and
- witch hazel.
